| 摘要 |
A PVA film that satisfies expressions (I) and (II), which has satisfactory stretchability and from which a polarizing film can be efficiently produced; and a process for film production which comprises (a) ejecting a PVA-containing film formation dope in a film form onto the first drying roll of a film formation device equipped with a plurality of drying rolls, partly drying the web, and then successively drying the web with the subsequent drying rolls to produce a film, wherein (b) the ratio of the peripheral speed (ST) of the drying roll on which the volatile content of the PVA film has fallen to 13 mass% to the peripheral speed (S1) of the first drying roll, ST/S1, is regulated to 0.990-1.050, (c) the ratio of the peripheral speed (SL) of the last drying roll to the peripheral speed ST, SL/ST, is regulated to 0.960-0.980, and (d) the SL/S1 ratio is regulated to 0.970-1.010. ?n(MD)Ave-0.1×10-3=?n(TD)Ave=?n(MD)Ave+0.25×10-3 (I) ?n(TD)Ave=2.5×10-3 (II) [In the expressions, ?n(MD)Ave indicates the value obtained by averaging the machine-direction birefringence values of the PVA film with respect to the film thickness direction, and ?n(TD)Ave indicates the value obtained by averaging the transverse-direction birefringence values of the PVA film with respect to the film thickness direction.] |
